Airplane warning system



P 1952 L. M. GREENE 2,611,310

AIRPLANE WARNING SYSTEM Filed Feb. 18, 1950 INVENTOR.

[6min GR'nvF .4 ro/zA/sy Patented Sept. 23, 1952 UNITED STATES PATENTOFFICE AIRPLANE WARNING SYSTEM Leonard M. Greene, Scarsilale, N. Y.

Application February 18, 1950, Serial No. 14 L986 1 Claim.

This invention relates to airplane warning systems. More particularly,my invention pertains to aural warning systems for airplanes.

At the present time it is customary to advise an airplane pilot ofcertain dangerous condi tions. Typical of these conditions are failureto lower the wheels before landing and assumption by an airplane of astall-approaching attitude with respect to a local air mass.

Heretofore the pilot usually was warned of such condition of imminentdanger visibly, as by lighting or blinking of a lamp, tactually, as byshaking the control stick, or aurally as by sounding of a horn orbuzzer. It is preferred to give the signal aurally since, under properconditions the pilot cannot fail to perceive it as he might a visiblesignal and since present-day tactual signalling mechanisms areexpensive, heavy, awkward and complicated, require considerable power,and often cannot fit into the space available. However, conditions arenot always proper for hearing aural signals. For example, a pilot oftenwears earphones during flight and these, or the cups in which they aremounted, shut the pilot off from the noise of his surroundings so that,unless the aural signal is very loud, he cannot hear it. On the otherhand, if the signal is loud enough to be heard by a pilot wearingearphones, it is much too loud for the pilot when the earphones areremoved. Moreover, on occasion, due to the relative volumes at thepilot's ear of the aural warning signal and a radio loudspeaker, theloudspeaker may drown the aural warning signal.

It is an object of my invention to provide an airplane aural warningsystem which is not subject to the foregoing defects.

More specifically it is an object of my invention to provide an airplanewarning system of the character described which imparts an aural warningby way of the electro-sound translating output device or devices of theairplanes radio.

It is an ancillary object of my invention to provide an airplane warningsystem of the character described which sounds at least two warningssimultaneously, one in the earphones, this optionally being of a lowmagnitude of sound sufficient only to give notice to the wearer of theearphones, and the other a horn or buzzer cockpit warning which is loudenough normally to be heard by anyone in the cockpit not wearingearphones.

It is another ancillary object of my invention to provide an airplanewarning system of the character described which imparts an aural warningin the earphones and loudspeaker so that, regardless of any possiblecondition, the warning will be heard.

It is another object of my invention to provide an airplane warningsystem of the character described which comprises relatively few andsimple parts, is easy to manufacture and inexpensive to install, and ishighly effective in operation.

It is another object of my invention to provide an airplane warningsignal of the character described which is of such construction that itis normally isolated from the radio except during warning conditions.

Otherobjects of my invention will in part be obvious and in part will bepointed out hereinafter.

My invention accordingly consists in the features of construction,combinations of elements and arrangements of parts which will beexemplified in the device hereinafter described and of which the scopeof application will be indicated in the appended claim.

The single figure illustrates one of the various possible embodiments ofa warning system constructed in accordance with my invention.

In said system the reference numeral 10 denotes a device which isresponsive to the imminence of danger. Said device includes an electricswitch 12 which preferably is of the normally open type and, desirably,is snap-acting. By way of example the device may be one such as isillustrated in my United States Letters Patent for Stall Warning Devicefor Airplanes, No. 2,478,967, dated August 16, 1949. Said deviceconstitutes a vane 14 whose forward edge is free and juts a slightdistance from the wing into the air stream. The vane is pivoted adjacentits rear edge and is arranged to operate the switch 12.

Said vane is located on the leading edge of the wing within the range ofinfluence of the shifting separation point, being so disposed that itwill move suddenly from the position it occupies during normal flight toanother position upon the approach of the separation point to apredetermined angle ahead of stall. Thus, when the airplane approaches astalling attituda'the vane will flip from one to another position and inso doing will cause the normally open contacts of switch l2 to close.

It will be understood that the switch 12 may form a part of some othercondition responsive device, as for example it may form part of alanding gear warning. In such cases the switch example.

is closed when the landing gear is up, is adjacent an operating part forthe landin gear, and is in series with a throttle switch which is openas long as the throttle control is above a certain position. When thethrottle control moves below this position its associated switch closesand, ii the landing gear is not fully down, the circuit through bothswitches is completed.

One contact ofthe switch 12 is connected to ground by a lead wire 16.The conductive fuselage of the airplane may serve as a ground andconstitute the return or neutral lead to one side, for instance thenegative side, of a battery It or other suitable source of power whichis grounded by means of a lead wire 20.. The'other' contact of theswitch I 2 isconnected tothe, opposite pole of the battery through alead wire22, switch 24, a lead wire 25, a vibrating type sounder 28 anda lead wire 38. V

I The switch 24 is of the single pole double throw 'type and is used iortesting and turning ofrthe .is energized it pullsthe contacts apaipmusinterrupting its energizingcircuit. By adjustment of the contact spacingand tension of the spring, the irequency of vibration can be varied.Optionally "a condenser; 40 may be shunted across the'contactsitz e hieof e cont ts brmi-n m iri spa k n It will be-appreoiated thatthesounder-fl desirably is of such physical'construction as to emit anaudible warning which can be heard clearly and-easily by the pilotjovertliencjrmal; cockpit noises when the pilot is not vea 'ing earphones.Itwillbeappreciated further that any of the u types i ia n e ssi ntensed he one shown here being illustrated merely by way-of wherein acam rotates incontact with a -plate and also; includes apair of;contacts;which are rapidly opened and closed during rotationof the cam.

, From the means a Waite e enstates when the switch closed initsleftj-hand position and when the airplane approaches the condition towhichthe device i0; is responsive, the sounder will emanate anauralwarning, I

The airplane has; a radio- .42 whoseputput is delivered toa pair ofwires 34,45 running 'to a double-pole,'doubleethrow switch A801 anyother equivalent type of switchwhichenables the'radio selectively toenergize either aloudspeaker 5,9 -'or a pair of earphones 52hr bothby'use' of a suitable type oi switch; i: e. a double jack.

In: order to irnp'ress a s'ign'al ffroTd-the sounder 28 across theoutput of the radio, I cbrinec'tone 34' to prolong Thus the sounder canbe cf the; type -upon approach to a specified dangerous condition, e. g.stall, the device it) is actuated by operation of the vane it to closethe normally open contacts of switch !2. This causes the sounder 28 tobe energized and will apprise the pilot of the imminence of danger. If,however, the radio should be on, its output emanating either through theloudspeaker or through the earphones may drown the warning of thesounder were the'present novel system not; employed.

Nevertheless, the warning-will be heard-over that sound outputdevice.ofv the "radidwhich happens to be' in operationforboth if suchbethecase. Moreover it will be heard in such device even if the radio is notoperating. ".[hi s occurs because,

as soon as switch l2vis closed, a circuit is'complet'ed from said switchthroughtherelay"opcratin coil 86 to; the battery. "Energization oftherelay coil closes the jpairfof contaotsflfifi, 62, thus jcornpletingthe circuit from 'the"sounder solenoid 38 to the outputoftheradio. H

When the sounder opensand'closesits contacts 32, fi l, the'condenser E01 and sounder solehold as W111 impress in the radio 'outputa potentialwhich ismodulated' at the audio frequency of the sounder. Said"potential will be translated into sound at the loudspeaker and/or'ear-1 phones. Since the superimposed signal isof the sam frequency as thesounder signal, it will be recognized by the pilot as the warning of thesounder to which he has been trained to take appropriate correctiveaction. V v I Attention'isdimcted to the fact that, until the "switch i2'hasbeen'closed, no'extraneous' electric impulses will bei'mposeduponthe'radio output.

This is due to the fact that themeans 'io'riinpre'ssing the signalinther'adio outputisn'ot connected to said output until such timejas the"switch 12 is closed. That is ,tojsaypnljessj the switch I2 is closedthenormally openipainof "contacts 55, '62 will isolate the"radiooutput.

If'itisdesilecl to check the "sounderjand coil 66, the switch 25 isswung to its righthand -position. This should energize said coil and thesounder 23, causing a warning signalto be'heard in the loudspeaker jand/or' earphones.

fl't. thus will be 'se'en that I 'haye'provided a device 'whichachievesall the bbjje'ctsofi invention and is well adapted to meet theconditions of pra'cticaluse. V g 4 H As various possible embodimentsmight be made of the above invention, and as various changesjmight bemade in the embodiment above s'e't forth, it is to be understood "that'allmatter herein describedor shown in the accompanying drawing, is to beinterpreted as illustrative and "not in a limiting sense.

Having thus described my menu-tn, I claim asnew and desireto secure byLetters Patent:

p I For use in fan airplanehavinga'radio and a source of electric power,and whereihfanactuator is provided which upon the imminence b fdanger cs "sw tch: that ompl t fc ff t "source 'of-power: an electricallyactuable-sounder,

means to connect said sounder in series in the circuit between theswitch and the source of power, said sounder including a pair ofcontacts in the circuit of the sounder and means to rapidly open andclose said contacts at an audio frequency when the sounder is actuated,a relay having an operating coil and a normally open switch which isarranged to be closed upon energization of said coil, means to connectsaid coil in the circuit between the switch and the source of power, andcircuit means to impress the potential of said contacts upon the outputof the radio,

. 6 said last-named means being connected to the radio output throughsaid relay switch.

LEONARD M. GREENE.

REFERENCES CITED The following references are of record in'the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,051,827 De Florez Aug. 25, 19362,386,992 Trott Oct. 16, 1945 2,552,331 Lamb May 8, 1951

